1. Field of the Invention
The invention relates to a method of joining a first member comprising at least a ceramic and a second member comprising a metal or a metal composite, and a joined body thereof.
2. Related Art Statement
In semiconductor processing systems, such as CVD, sputtering and etching, a semiconductor wafer is mounted on a susceptor. The wafer is then processed by generating plasma in a process chamber, or by heating a reaction gas so that the gas is dissociated. It has been known to use a ceramic electrostatic chuck as a susceptor and to adsorb the wafer onto the susceptor while the wafer is processed. It has been also known to use a ceramic heater as a susceptor and to mount the wafer on the heater, which is directly heated. It is necessary to reduce the temperature change during the processing of the wafer on the susceptor, for improving the productivity of the wafer. For this, it is necessary to cool the wafer to compensate for the incidence of heat due to plasma generation so that the temperature of the wafer is controlled. A cooling system is thus connected with the susceptor.
A technique for joining an electrostatic chuck with a cooling board of water cooling system by means of metal flange has been proposed (Japanese patent laid-open publication 3-3249A). According to the technique, an electrostatic chuck made of alumina is bonded with a cooling flange made of aluminum with indium. According to Japanese patent publication 4-287344A, a susceptor and a metal cooling board are joined with each other by means of a paste-like silicone resin.
When indium or silicone resin adhesive compositions are used as an adhesive for joining a ceramic electrostatic chuck and a water cooling flange made of metal, however, insufficient pressure during the joining process may deteriorate the flatness of the semiconductor wafer adsorption face of the chuck. The wafer is adsorbed onto the adsorption face of the chuck during the processing of the wafer. If the flatness of the adsorption face is deteriorated, the chuck may be out of specification so that the production yield is reduced. Moreover, when a back side gas is supplied between the back face of the semiconductor wafer and the chuck, there would be a risk that the gas might leak along the joining interface of the chuck and cooling flange. In particular, thermal cycles are applied in a system for producing semiconductors, and it is demanded to secure the air-tightness along the joining interface between the chuck and flange with excellent reliability. It is thus preferred to apply a pressure during the joining process. On the other hand, when the pressure during the joining process is too large, adhesive may leak outside the joining interface of the chuck and cooling flange. Further, the thickness of the adhesive may not be uniform or may be changed among articles actually produced.
For the above reasons, it is demanded to improve the air-tightness of the joining interface, to prevent adhesive leakage and to improve the adhesion along the interface of the adhesive layer and chuck when the chuck and metal member are joined. Particularly, it is difficult to adequately wet a ceramics with an adhesive, so that it is difficult to improve the adhesiveness along the interface microscopically.